Chemistry Paper 2 Consolidation Flashcards
The amount of water vapour in today’s atmosphere is much less than the amount in the Earth’s early atmosphere.
Explain why the amount of water vapour in the atmosphere has decreased.
- Earth cooled / temperature decreased
- Water vapour condensed / oceans formed
Describe what you would see if damp, blue litmus paper is placed into chlorine gas.
Litmus paper turns from blue to red first, then from red to white
Describe what is meant by a covalent bond.
- Shared electrons
- A pair of / two electrons
Explain why chlorine is a gas, rather than a liquid, at room temperature.
- Intermolecular forces / forces between molecules
- Intermolecular forces are weak and take little energy to break
- Chlorine has a boiling point below room temperature
When the gas hydrogen chloride, HCl, is dissolved in water, a solution forms. Blue litmus paper dipped in this solution turns red.
State why the litmus paper turns red.
Solution is acidic and contains H+ ions
Explain the trend between the alkanes’ boiling points and the no. of carbon atoms in one molecule of each alkane.
- Boiling points increase as the number of carbon atoms (per molecule) increases
- Because stronger forces between molecules / increased intermolecular forces
Describe what is seen when chlorine water is added to potassium bromide solution and the mixture shaken.
- Potassium bromide solution is colourless
- Mixture turns yellow/ orange
A solid ionic compound is dissolved in water to form a solution.
Describe a simple experiment to show that charged particles are present in this solution.
- Insert electrodes into aqueous solution
- Connect to electrical supply
- Bulb lights
Explain why the mass of products might be greater than the mass of reactants in an experiment.
Other gases could have also reacted
Explain how carbon dioxide is released into the atmosphere
Complete combustion of fuels/wood/rubbish/plastic
Iron reacts with oxygen to form iron oxide, iron wool was placed in the bottom of a wet test tube. The test tube was then put in a beaker of water. After some time the water level in the test tube rose and some of the iron wool had formed an iron oxide.
Explain why the water level in the test tube rose during the experiment.
- Oxygen is removed from air to oxidise iron
- Water rises to fill space
Iron reacts with oxygen to form iron oxide, iron wool was placed in the bottom of a wet test tube. The test tube was then put in a beaker of water. After some time the water level in the test tube rose and some of the iron wool had formed an iron oxide.
What gas would mostly remain in the test tube at the end of the experiment?
Nitrogen
Lithium, potassium and rubidium are alkali metals.
Describe what you would see when a small piece of rubidium is dropped onto water.
- Effervescence
- A flame is ignited
Explain, in terms of bond breaking and bond making, why some reactions are exothermic.
- Breaking bonds needs energy, which is provided from endothermic reactions
- Making bonds releases energy, which is done in exothermic reactions
- More energy is released than absorbed in an exothermic reaction
Bromine reacts with hydrogen to form hydrogen bromide. Hydrogen bromide dissolves in water to form a solution.
State the name of the solution formed.
Hydrobromic acid
Elements in group 3 of the periodic table are boron, aluminium, pallia, indium and thallium. Elements can declassified as metals or non metals.
Explain, using its position in the periodic table, whether indium is a metal or a non-metal
- Metal
- Indium is on the left/ below the line dividing metals and non-metals
Describe what would be seen when a piece of calcium is dropped into a container of water.
- Effervescence as hydrogen is produced
- A white precipitate is formed as calcium hydroxide appears
Magnesium oxide has a melting point of 2852 degrees Celsius.
Explain why magnesium oxide has such a high melting point.
A large amount of energy is required to overcome the strong electrostatic forces between 2+ cations and 2- anions
Describe the properties of an alkane and an alkene.
- Alkane is a saturated molecule that contains a single covalent bond between two carbon atoms
- Alkene is an unsaturated molecule that contains a double covalent bond between two carbon atoms
Sodium thiosulfate solution, Na2S2O3, reacts with dilute hydrochloric acid. Na2S2O3 (aq) + 2HCl (aq) → 2NaCl (aq) + H2O (l) + SO2 (g) + S (s). When dilute hydrochloric acid is mixed with sodium thiosulfate solution, the mixture turns cloudy.
Explain why the mixture turns cloudy.
A solid sulphuric precipitate is formed
In an investigation, different concentrations of hydrochloric acid are reacted with sodium thiosulfate solution. The mixture goes cloudy at different rates.
Describe how the rate at which the mixture goes cloudy can be measured.
- Flask placed over/ in front of cross
- Measure time when cross is obscured
What are the three most common gaseous elements in air?
- Nitrogen
- Oxygen
- Argon
The flask is used for an experiment to find the density of argon. The flask holds 250.0 cm^3 when filled up to the line. There is an error in the volume the student has used in the calculation. This would give an incorrect value for the density of argon.
Identify this error and state what should be done to correct it.
- Volume of flask is more than 250 cm^3
- Measure the whole volume of the flask
Explain what is meant by a dynamic equilibrium.
- Forward and reverse reaction occurs simultaneously at same rate with same concentration
- No observable change
The reaction between nitrogen and hydrogen to form ammonia is exothermic. The temperature used is 450°C.
Explain how the use of a lower temperature would affect the equilibrium yield of ammonia.
- Lower temperature favours forward reaction
- Because forward reaction is exothermic
- Hence yield increases
When there are alternative methods of producing a product, the final pathway is chosen by considering atom economy, cost of energy, yield of product and rates of reactions.
State another factor that should also be considered.
Equilibrium position
When nitrogen reacts with hydrogen, the amount of ammonia gradually increases until it becomes constant.
Explain why the amount of ammonia remains constant.
- Forward and reverse reaction occurs simultaneously at same rate with same concentration
- Reaction is in dynamic equilibrium
The minimum volumes of nitrogen and hydrogen that must react completely to form 5000 dm^3 of ammonia are calculated. These volumes are mixed and left, under appropriate conditions, until the reaction reaches equilibrium.
Explain which gas or gases will be present when equilibrium is reached.
- Nitrogen, hydrogen and ammonia
- Because the reaction is a reversible reaction
Explain the effect on the equilibrium yield and the rate of equilibrium, if the Haber process is carried out at a pressure higher than 200 atm.
- Increased equilibrium yield and rate
- Because gas molecules are more concentrated
- Increased frequency of collisions
Why can ionic compounds only conduct electricity in molten form?
Because ions become delocalised and are free to move, causing charge to flow
Explain how the greenhouse effect is caused by the gases produced by the complete combustion of diesel oil.
- Carbon dioxide and water produced in complete combustion
- Carbon dioxide and water are greenhouse gases and absorb long wavelength radiation from the Sun
- Greenhouse gases re-radiate long wavelength radiation to the Earth’s atmosphere
- Causing increase in temperature
Explain how the electronic configuration of an atom of potassium is related to its position in the periodic table.
- Number of electrons on outer shell gives the group number
- Number of electron shells gives the period number
Two gas syringes are connected by a glass tube.
Inside the glass tube there are some pieces of zinc.
Zinc reacts with oxygen at a temperature of over 225 °C.
Not all the oxygen reacts at once, the oxygen reacts only when in contact with the zinc.
Devise a plan to find the volume of oxygen contained in a known volume of air.
- Heating tube where zinc is
- Pass air over heated zinc
- Until no further change in volume
- Measuring volume of gas after experiment and calculate difference in volume
Some pieces of calcium carbonate were added to dilute hydrochloric acid in a conical flask and the volume of carbon dioxide produced was measured. The reaction between calcium carbonate and dilute hydrochloric acid was investigated at different temperatures.
State what could be used to keep the temperature of the conical flask and its contents at a temperature of 45 °C throughout the reaction.
Conical flask in water bath
Explain why the incomplete combustion of pentadecane can produce carbon monoxide as one of the products.
Insufficient oxygen supply to oxidise all carbon to carbon dioxide
Explain how carbon monoxide behaves as a toxic gas
- Carbon monoxide combines with haemoglobin in red blood cells
- Prevents oxygen from being carried into the bloodstream
Explain why water droplets form on the bottom of the beaker of cold water in an experiment which methane gas is burned.
- Water vapour forms during combustion
- Water vapour condenses on cold surface
